Phenols are readily alkylated by reaction with olefins using an aluminum phenate catalyst (Ecke et al, U.S. Pat. No. 2,831,898). When this process is used to introduce sec-alkyl groups, higher temperatures are required compared to the introduction of tert-alkyl groups. Aluminum remaining in the reaction following the alkylation is particularly difficult to remove from such sec-alkylphenol compositions. For example, residual aluminum can be removed from tert-alkylphenol compositions by washing with aqueous acid under moderate conditions, but when this is applied to sec-alkylphenol compositions the aluminum is not removed without resorting to refluxing the sec-alkylphenol with the mineral acid.